The present invention concerns a remotely actuated park/lock mechanism configured to prevent accidentally shifting a transmission out of the park position.
With recent advances in electronics and the subsequent integration of electronics into vehicle systems, many functions historically performed mechanically are now candidates for conversion to electronic devices or electromechanical devices. Such functions relate to engine and transmission control (more broadly called "power plant management"), antilock braking, steering, passenger compartment climate control, and the like. In regard to the present device, some vehicle manufacturers are considering using electronic controls to control transmission shifting, and are considering mechanically decoupling the transmission shifter completely from the vehicle transmission. Proponents of an "all electrical" shift system argue that it has advantages in terms of lower part and assembly cost, simplified routing of parts from the shifter to the transmission, reduced warranty, and improved customer satisfaction, including possible customization of the vehicle shift pattern and feel for specific customer preferences. However, sometimes manufacturers still want a direct mechanical link of some kind. A reason is because a shifter that is not mechanically coupled in some way to a transmission has a disadvantage in that mechanical couplings physically prevent accidental shifting. Additionally, new systems always introduce new problems. For example, an "all electronic" system must be designed to safely deal with a dead battery, low electrical voltage/low power in the vehicle, unexpected total loss of electrical power (while parked or while driving), towing situations, and countless other scenarios. One problem in particular occurs in electrically controlled automatic transmissions with torque converters, because the automatic transmission characteristically is rotatable when the transmission is in a drive gear (e.g., drive or reverse) and the engine is off. Therefore, these transmissions must have a mechanical or electromechanical park/lock device that fixes the transmission gears against rotation to prevent a parked vehicle from simply rolling away, even if vehicle electrical power is lost. Another concern is that federal regulations require that certain predetermined vehicle conditions be met before a shifter can be shifted out of the park position. Many manufacturers satisfy these federal regulations through use of a brake-ignition-transmission-shift-interlock (BITSI) device, which physically holds a shift lever in the park position until the predetermined vehicle conditions are met. However, a BITSI system must be able to perform its function satisfactorily and positively, including vehicle "power on" and "power off" ignition conditions, as well as if the vehicle power source goes dead.
One advantage that the proponents of an "all electrical" shifting system point to is elimination of a Bowden transmission shift cable or mechanical linkage. Many modern passenger vehicles have transmission shifters with a pivotable shift lever mechanically connected to a vehicle transmission, such as by a Bowden cable or mechanical linkage. Recently, many vehicle manufacturers have incorporated park/lock mechanisms into the shifters for automatic transmissions to prevent movement of the shift lever out of the park position unless certain predetermined vehicle conditions are met. However, it is difficult to control quality and functionality of a shifter-mounted park/lock mechanism in an assembled vehicle since the shifter manufacturer, the Bowden cable manufacturer, the transmission manufacturer, and the vehicle assembler are all typically different companies.
I have conceived of integrating a park/lock mechanism with a remotely operated actuator directly into the vehicle transmission, which provides many of the advantages of the existing mechanical and electromechanical park/lock systems, but without the problems associated with Bowden cables. This allows the transmission manufacturer to substantially control the entire system in terms of functionality and quality. Advantageously, my invention integrates the park/lock mechanism directly into the vehicle transmission and links it directly to the transmission component that prevents accidental rotation of the transmission gearing, so that several parts are eliminated. Still further, the overall assembly is improved such as by elimination of the assembly steps of installation and hookup of Bowden cable or other mechanically operated transmission linkage. Even more broadly, I have conceived of a hydraulically activated and/or electrically controlled park/lock mechanism where the electrical connection between a shifter and its transmission have totally eliminated the need for a mechanical connection between the shifter and the transmission.
Accordingly, an apparatus solving the aforementioned problems is desired.